I was late on my oil change (about 5k instead of my normal 3k). Seemed to be going routinely til I pulled my filter to replace it and found half of a O-ring in one of the entry passages. The piece was about a cm in overall length, real thin, probably a mm or 2 tops, and one side was smooth while the other was very rough. I'd estimate from the curvature that it is probably about the diameter of a penny when whole. Any idea where this could be from? Engine seems to be running fine and oil pressure is the same as always. I guess I'm worried the most about my engine bearings, but it seems pretty rare to spin bearings on these engines. I've always had a bit of a fuel dilution issue since I'm a noob and didn't do my side seals correctly.

S5 TII rebuilt by me. Has ~65k miles on it, many of them auto-xing.

Thoughts? Rebuild? Just keep driving it until I notice an oil pressure problem?

edit: has Atkins front oil bypass thingy (forget what its called)

 

front crossover o ring blew. the back up teflon oring should be ok since u have s5 block.

 

You are talking about between the front cover and the front iron that feeds the OMP, correct?

edit: or the one that leads from the pump to the oil cooler? I'd think there would be a pressure drop associated with losing that one.

 

Incorrect. If its a newer S5 block, it can loose that o-ring and still be fine as long as the gasket holds. See here.

http://mazdatrix.com/faq/oring.htm

 

Ok, thanks for clearing that up! So as long as my oil pressure is good then I am good to go since there is still the teflon and the gasket itself?

 

yes.

but dont forget to change your oil every 2000 miles.... jajaja

 

Do NOT be fooled by good oil pressure. Pressure is an indication that your pump is working, but it does not necessarily mean that you have good flow. In the case where I lost my front cover o-ring, my pressure was actually a little on the higher side of normal. The o-ring was actually restricting flow, driving the pressure up.

What I am saying is that you only found half the o-ring. If it were me, I would be pulling the front cover, to find the other half. I would not be happy until I found the rest of it. It could be floating around somewhere, between the front cover and filter.

 

Yeah, the more I think about it, the more I am leaning towards a front cover pull. Assuming is a bad idea, even if the engine has been doing fine for several thousand miles without it.

 

I'm not following how an o-ring would be forced into the high pressure passage without any pressure from the outside. There is high pressure in the passage and low pressure outside... if it failed, you'd think it would do so in the opposite direction and then only if it could get past the backup ring and gasket.

Where was the o-ring lodged at blocking the flow and increasing pressure out of curiosity?

 

it will eventually go into your oil filter.

you dont have to pull the front cover off. unless you do your own wrenching and willing to take few hrs cleaning and reinstalling.

did you check the filter itself when you found thew half oring in the passage?

 

It couldnt make it to the filter.Oil comes out to the front cover and down to the front regulator.That o ring came from somewhere else

 

Hmm... my car seems to think differently...

Anyway, I found my o-ring under the oil filter, when getting my oil changed. I really need to look at the oiling diagram, but I am *assuming* that the oil pressure sender is between the oil pump and the inlet to the oil filter.

When finding the o-ring, I pulled apart my front cover, as I had low oil pressure after the oil change. I found that the o-ring was missing. This was on a 88 N/A.

 

You know, I am not really following that statement... you do realize how the front regulator works, right?

 

If you have the earlier front side housing style, assemble the front of the engine with the O-ring, no front cover gasket, (use silicone instead), and maybe a little Hylomar to hold the O-ring in place during assembly (and throw away the white teflon ring that comes in the gasket set). If you really WANT to use a gasket, then use the 79-85 one, which needs to be purchased separately.

If you have the later style front side housing, use the gasket, rubber O-ring, and white teflon O-ring (and we prefer some silicone) --- gasket CAN be left out, and use silicone in place of it.


Actually I believe they are referring to the front cover gasket, not the front cover o-ring.

 

No, you use the different gasket because it's thicker in that area. The problem is with the O-ring, they just say to use a different gasket because of the o-ring problem. The o-ring doesn't have enough room to properly seal the area. The gasket helps hold the o-ring in place assuming the teflon seal is used. If not, thats why they recommend the 79-85 gasket as it wasn't used with the teflon ring.

Regardless, I'd recommend taking the front cover off and replacing the bad parts. No need to loose a engine over a o-ring.

Out of curiosity, are you running a oil filter pedestal?